The present invention relates to a process and a device for manufacturing synthesis gas usable for producing for example ammonia, methanol, urea, hydrocarbons, etc.
The gases obtained according to the invention may be converted and then possibly purified or else be used as reducing gases.
It is well-known that synthesis gas is obtained by the reaction of a mixture of hydrocarbons or fuel with an oxidant.
A first way of producing synthesis gas consists in associating a primary reforming reactor with a secondary reforming reactor. The primary reforming reactor conventionally consists of pipes filled with catalyst and heated either through an external combustion or through heat exchange with warm effluents, for example with those of the secondary reforming reactor. The hydrocarbon is generally introduced into the primary reforming reactor with a large excess of steam.
The primary reforming effluents are then introduced into the secondary reformer which also receives an oxidant supply.
U.S. Pat. No. 3,278,452 describes a secondary reformer whose improvement consists of an additional introduction of oxidant between the catalytic beds arranged successively in this reactor. However, the improvement provided by the stepped lay-out of the oxidant does not solve the major drawback of this type of reactor which requires a high amount of excess steam whose production is costly. Moreover, steam presents the disadvantage of changing the distribution between the hydrogen, the carbon dioxide and the carbon monoxide present in the synthesis gas.
Another way of manufacturing synthesis gas, with a low steam consumption, consists in performing a partial oxidation of the hydrocarbons.
U.S. Pat. No. 4,699,631 describes such an example of a reactor working without a catalyst, by means of a flame. However, this type of reactor always produces a certain proportion of soot because combustion is carried out with a lack of oxygen, and subsequently this reactor requires costly cleaning. Besides, if the amount of soot is to be reduced, the oxygen consumption has to be raised, which decreases the reactor efficiency. Thus, although working with little steam, this type of reactor has the drawback of the formation of soot when the oxygen consumption is reduced or when working in air.
FR-2,638,443 describes another process for producing synthesis gas by means of a flame, with the partial oxidation of light hydrocarbons.